Question

Passive water absorption by root system is due to
(a) Force created in roots
(b) Osmotic force in the shoot
(c) High respiratory activity of root
(d) Tension in sap due to transpiration

Answer 1

If there is water loss by a process involving the exhalation of water vapour by stomata, roots take up the passive absorption of water. This raises the suction pressure in general. Water is thus absorbed from neighbouring leaf xylem vessels and this induces a strain in the fluid that is transferred into the cells of the xylem.

Complete step by step answer:
The process of passive water absorption is carried out without the use of metabolic energy. Here, as an organ of absorption or passage, only the roots function. It occurs during the daytime in rapidly transpiring plants, due to stomatal opening and atmospheric conditions. The force for water absorption is produced at the end of the leaf, i.e. the transpiration pull. The main explanation behind this transpiration pull is that in the plant axis, water is raised up like a bucket of water is raised from a well by a human. Transpiration pull is responsible for pulling water at the end of the leaf, the pull or force in the xylem elements is transferred down to the root via the water column. Because of the cohesion between the molecules, the consistency of the water column stays intact and it functions as a chain.
So, the correct answer is, ‘(d) Tension in the sap due to transpiration’.

Note: Water is absorbed by the root system from the soil, and often by root tips. In plants, there are two separate water absorption mechanisms such as active water absorption and passive water absorption. Active water absorption is absorbed by root activity itself. Via the root cells that can be found in the roots where mainly passive absorption occurs, the water can reach the plant. Along with the absorption of water, they also absorb minerals and nutrients.